Unilateral moveable interbody fusion device and method of use

ABSTRACT

An interbody fusion device including a body member, at least one side member engaging the body member, and at least one movement mechanism that engages at least one side member and the body member. A surgical method for maintaining a space between two vertebral bodies in a spine, including the steps of obtaining a medical device, such as an interbody fusion device, and inserting and coupling an expansion tool into an opening within the medical device. The surgical method also including slidingly inserting the medical device into a space between two vertebral bodies and rotating the expansion tool to move the at least one side member in a direction relative to the body member. The method may further include detaching the expansion tool from the medical device and removing the tool from the space between the two vertebral bodies in the spine.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority benefit under 35 U.S.C. §119(e) of U.S.provisional patent application No. 61/570,613 filed Dec. 14, 2011, whichis incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates generally to general surgery, orthopaedicand neurosurgical implants used for insertion within a space betweenhard tissue structures, and more specifically, but not exclusively,concerns devices implanted between bones to replace a resected,fractured or diseased structures and to maintain or reestablish properspacing between two bones.

BACKGROUND OF THE INVENTION

Damage or disease that affects the integral structure of a bone or otherstructures, may lead to neurologic impairment or loss of structuralsupport integrity with possible permanent damage to the surrounding softtissue and adjacent neurologic, vascular and systemic structures.Maintaining or reestablishing anatomic spacing within a bone structureor other structural tissue is critical to ensuring continuedfunctionality and mobility of the patient and avoidance of long-termserious neurological, vascular or other systemic impairments. Pleasenote that the terms “implant” and “device” may be used interchangeablyand have the same meaning herein.

SUMMARY OF THE INVENTION

Advancement of the state of interbody fusion devices and implants andthe surgical management relating to the clinical presentation of damagedtissue structures within the body is believed desirable. Exampleembodiments of the invention that satisfies the need for improvements toan expandable interbody fusion device used to treat patients sufferingfrom either diseased or damaged disc or other tissue structures includesat least one moveable side member coupled to a body member.

The present invention provides in one aspect, an interbody fusion devicehaving a body member, at least one side member engaging the body memberand at least one movement mechanism engaging the at least one sidemember and the body member.

The present invention provides in another aspect, a surgical method formaintaining a space between two vertebral bodies, the method may includethe step of obtaining a medical device having a body member with atleast one side member engaging the body member. Also included is atleast one movement mechanism engaging the at least one side member andthe body member. The method may include the step of inserting andcoupling an expansion tool into an opening within the medical device andalso slidingly inserting the medical device into a space between twovertebral bodies. The method may include the further step of rotatingthe expansion tool to move the at least one side member in a directioneither away from or towards the body member.

Further, additional features and advantages are realized through thetechniques of the present invention. Other embodiments and aspects ofthe invention are described in detail herein and are considered a partof the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other objects, features andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a perspective view of one embodiment of a unilateral,horizontal expandable interbody fusion device, in accordance with anaspect of the present invention;

FIG. 2 is an inferior view of another embodiment unilateral, horizontalexpandable interbody fusion device with the moveable member retracted,in accordance with an aspect of the present invention;

FIG. 3 is a superior view of the expandable interbody fusion device ofFIG. 1 with the moveable member extended, in accordance with an aspectof the present invention;

FIG. 4 is a side view of the expandable interbody fusion device of FIG.1, in accordance with an aspect of the present invention;

FIG. 5 is a front view of the expandable interbody fusion device of FIG.1 with the moveable member extended, in accordance with an aspect of thepresent invention;

FIG. 6 is a front, exploded view of the expandable interbody fusiondevice of FIG. 1 and an expansion tool, in accordance with an aspect ofthe present invention;

FIG. 7 is a side, exploded view of the expandable interbody fusiondevice of FIG. 1 and the expansion tool, in accordance with an aspect ofthe present invention;

FIG. 8 is a cross-sectional view along the transverse plane of theexpandable interbody fusion device of FIG. 1 and the expansion tool, inaccordance with an aspect of the present invention;

FIG. 9 is a perspective view of another embodiment of a unilateralexpandable interbody fusion device, in accordance with an aspect of thepresent invention;

FIG. 10 is a superior view of the expandable interbody fusion device ofFIG. 9 with the moveable member completely retracted, in accordance withan aspect of the present invention;

FIG. 11 is a side view of the expandable interbody fusion device of FIG.9, in accordance with an aspect of the present invention;

FIG. 12 is a front view of the expandable interbody fusion device ofFIG. 9 with the moveable member partially extended and the toolinserted, in accordance with an aspect of the present invention;

FIG. 13 is a side, exploded view of the expandable interbody fusiondevice of FIG. 9 and the tool, in accordance with an aspect of thepresent invention;

FIG. 14 is another side, exploded view of the expandable interbodyfusion device of FIG. 9 and the expansion tool, in accordance with anaspect of the present invention;

FIG. 15 is a cross-sectional view along the transverse plane of theexpandable interbody fusion device of FIG. 9 and the expansion tool, inaccordance with an aspect of the present invention;

FIG. 16 is a perspective view a movement mechanism of the expandableinterbody fusion device of FIG. 9, in accordance with an aspect of thepresent invention.

DETAILED DESCRIPTION FOR CARRYING OUT THE INVENTION

Generally stated, disclosed herein is an interbody fusion device orinterbody device that typically includes a body member, a threaded rodmember, a circular gear face, a support means, and a retractable member.The retractable member extending in a horizontal direction. As usedherein, the terms “interbody fusion device,” “medical device,” “device,”“interbody device” and “implant” may be used interchangeable as theyessentially describe the same type of device. Further, a correspondingexpansion tool used for expansion and contraction of the interbodydevice is discussed. Finally, described herein is a surgical method forusing the interbody fusion device to maintain a space between twovertebral bodies within a patient suffering from a diseased or damageddisc or spinal column.

As depicted in FIG. 1, the general arrangement of a unilateralhorizontal expandable interbody fusion device 100, in accordance with anaspect of the present invention, includes a body member 110 and one sidemember 120. In this detailed description and the following claims, thewords proximal, distal, anterior, posterior, medial, lateral, superiorand inferior are defined by their standard usage for indicating aparticular part of a bone or implant according to the relativedisposition of the natural bone or directional terms of reference. Forexample, “proximal” means the portion of an implant nearest the torso,while “distal” indicates the portion of the implant farthest from thetorso. As for directional terms, “anterior” is a direction towards thefront side of the body, “posterior” means a direction towards the backside of the body, “medial” means towards the midline of the body,“lateral” is a direction towards the sides or away from the midline ofthe body, “superior” means a direction above and “inferior” means adirection below another object or structure.

It is shown in FIG. 1, the example of the unilateral, horizontalexpandable interbody fusion device 100. The device 100 as seen in FIGS.1 and 2 may have, for example, a generally rectangular geometry withvarious configured long sides to facilitate insertion and bone coverage.Although it would be understood by one skilled in the art that otheroutside configurations can be used. For example purposes, the long sidesare arcuate although it is contemplated that other geometrical shapesmay also be used in the construct. The implant 100 may likely include atleast one moveable side member 120 and a body member 110. The sidemember 120 may be detachably coupled to the body member 110.

As seen in FIGS. 1, 3 and 7, body member 110 may have at least onethrough hole 111 for insertion of bone graft material disposed on theinferior and superior bone contacting surfaces 105. The hole 111 mayextend through the top and bottom surfaces 105 of the body member 110.The opening 111 typically extends through both bone contacting surfaces105 and into the inner cavity of the body member 110. The size andconfiguration of the opening 111 allow the surgeon to place bone graftmaterial inside the implant 100 to achieve a continuous fusion betweenthe inferior and superior vertebral bodies.

As shown in FIG. 2, an alternative embodiment of body member 110 mayalso have at least two marginalized openings 131 that may generallyextend through the top and bottom surfaces 105 of the body member 110and through the inner cavity of the body member 110. The size andconfiguration of the openings 131 allow the surgeon to pack bone graftmaterial inside the implant 100 to achieve a continuous fusion betweenthe inferior and superior vertebral bodies.

As seen in FIGS. 1, 4 and 7, side member 120 also may have at least twoholes 132 oriented in a horizontal direction. These holes 132 may beencircled by a cylindrical wall 114 projecting from an inner surface ofside member 120 to facilitate the orientation of the side member 120when it translates from a refracted to an expanded position andvice-a-versa. The wall 114 may also include a stop mechanism which mayinclude a horizontal slot and pin arrangement that keeps the side member120 from overextending and becoming disengaged with the body member 110.

As shown in the sectional view shown in FIG. 8, holes 132 include ameans for moving the side member 150. For example purposes, the meansfor moving the side member 150 may include sets of threads 134 disposedon the inner surface of holes 132 that are positioned within the sidemember 120. The threads 134 are configured to threadingly engage with atleast two threaded rod members 123. Rotation of threaded rod members 123will cause side member 120 to move either in an inward or outwarddirection relative to the body member 110. The overall width of theimplant 100 can be changed via the rotation of the threaded rod members123 and the corresponding unilateral movement of side member 120. It iscontemplated that other means for causing the controlled translation ofside member 120 to occur may include a ratcheting or a locking slidingmechanism.

As seen in FIGS. 6 and 7, threaded rod members 123 include a cylindricalportion 135 and a gear face or gear 136 with teeth. The means for movingthe side member 150 acts to convert rotational movement intotranslational movement. When assembled within body member 110, both gearfaces 136 are turned at the same time with a tool 400. Rotation of thegear faces 136 causes the threaded cylindrical portion 135 to turn,resulting in the translational movement of the side member 120 relativeto the body member 110.

Also shown in FIGS. 1, 2, 3 and 4 are the superior and inferior bonecontacting surfaces 105. For example purposes, bone contacting surfaces105 are shown having teeth-like or tine structures projecting away fromthe superior and inferior surfaces. Although not shown, it is understoodby one skilled in the art that modular bone contacting surfaces, caps orplates may be used to provide for varying types of bone contactingsurfaces and structures, including, but not limited to sharp tines,porous coatings, biomaterial/ingrowth surfaces and ridge structures.Further, it is contemplated that angled bone contacting surfaces, capsor plates may be attachable to address various clinical deformities thatare encountered clinically. It is also understood that the bonecontacting surfaces 105 may be coated with bioactive or bone ingrowthcoatings.

As shown in FIGS. 2 and 3, body member 110 may have, for example, agenerally rectangular shape with, for example, an arcuate outer side anda planar inner side that is positioned adjacent to side member 120 whendevice 100 is in the fully retracted position. Side member 120 may alsohave, for example, a planar inner side and an arcuate outer side.

FIGS. 3 and 5 show device 100 in its expanded position with housings 137with outer wall 114 that included inner threaded holes 132 spanning thegap between side member 120 and body member 110. Housings 137 arereceived into corresponding openings 138 (see FIGS. 7 and 8) in bodymember 110 when side member 120 is retracted and function to maintainalignment of the side member 120 both in the expanded and retractedpositions.

FIG. 4 is a side view of device 100 and shows the ridged bone contactingsurfaces 105. Except for the front aspect, the top and bottom surfaces105 appear to be substantially parallel to each other. It would beunderstood by one skilled in the art that such surfaces could also, forexample, be tapered or angled to address certain anatomic situations. Asnoted above, the front aspect of device 100 is shown to be tapered tofacilitate insertion into the intravertebral space. Several openings 133are shown that horizontally transverse both the side member 120 and bodymember 110. Openings 133 are typically filled with bone graftingmaterial following the implantation of the device 100 in vivo. Openings133 are also illustrated in FIG. 1 as openings 133 and opening 113,where the opening 113 within the body member 110 is the extension of oneof openings 133 in the side member 120 through to the body member 110.

The sectional view of FIG. 8, shows the two threaded rod members 123 inposition within the body member 110 while engaging the threaded hole 132of the side member 120 causing movement thereof. FIG. 8 shows housing137 inside openings 138 with a threaded hole 132 passing down the centerof housing 137. A support ring 125 acts to couple the threaded rods 123to maintain the static position of the means for moving the side member150 when rotated. Support ring 125 may, for example, be a snap ring orother similar type of structure that will nest within a notch 126 orother retainment mode within the inner cavity of the body member 110.

The device 100 also has a tool opening 140 (see FIGS. 5, 6 and 8) thatis sized to receive the expansion tool 400. The tool 400 has two sets ofteeth or cogs 401 that correspond to the teeth on the gear face 136. Theend of such a tool 400 would usually be inserted into opening 140 andwith the two sets of teeth 401 engaging the teeth disposed on the twogear faces 136 of the means for moving the side member 150. Rotation ofthe tool 400 by the user will cause both gear faces 136 to rotatecausing side member 120 to move as the two threaded rod members 123 areactuated. The sectional view seen in FIG. 8 shows the inserted tool 400with the two gear elements 401 engaged with the two corresponding gearfaces 136 of the threaded rods 123.

The biocompatible materials used to fabricate the dynamic horizontalimplant 100 could include, for example, a myriad of metals, polymers andcomposites. Examples of these include PEEK, titanium and stainlesssteel.

The example surgical method for using the interbody fusion devices 100is well known in the art, including the appropriate surgical exposureand dissection techniques. The method includes, obtaining the properlysized and configured device 100 relative to the target vertebral endplates that will be opposing the superior and inferior surfaces 105. Anexpansion or extension tool 400 is then inserted into the hole 140 ofthe device 100 to secure it for insertion into the spine. For examplepurposes only, we shall describe herein the technique as used in theinsertion between two vertebral bodies to maintain the disc space therebetween. The device 100 is usually slid from a lateral orposterior-lateral direction into the target disc space.

Following positioning of the device 100 within the disc space, theextension/expansion/insertion tool 400 is rotated causing the sidemember 120 to move away from the body 110 resulting in the overall widthdimension of the device 100 to increase or decrease, depending upon thedirection of the rotation of the extension/contraction means 150. Theuser will stop rotating the extension/expansion tool 400 once optimumsupport is achieved relative to the inferior and superior vertebralbodies.

The method may further include the step of detaching theextension/expansion tool 400 from the body member 110 and removing theinstrument from inside the living body.

It should be understood by those skilled in the art that the surgicalmethod described herein may also include alternatively, using modularbone contacting plates or surfaces which have been coupled in somemanner to an alternative embodiment of the body member 110 or sidemember 120 to accommodate various clinical deformities or bone growthcoatings.

Referring now to FIGS. 9-16, another embodiment of a unilateralexpandable interbody fusion device 200 is shown. The implant 200 maylikely include at least one moveable side member 202 and a body member204. The side member 202 may be detachably coupled to the body member204. The body member 204 may include a center through hole 206 and atleast two lateral through holes 208 extending through the top and bottombone contacting surfaces 210. The through holes 206, 208 may allow forinsertion of bone graft material to achieve a continuous fusion betweenthe inferior and superior vertebral bodies.

As seen in FIGS. 13-16, the body member 204 may include a medialreinforcement bar 224 on the medial side of the through hole 206 and twolateral bars 226 on the medial side of the through holes 208. The sidemember 202 also may have a medial channel 228 and at least two sidechannels 230 oriented in the horizontal direction. The channels 228, 230are configured to facilitate the orientation and alignment of the sidemember 202 as it translates from a retracted to an expanded position andvice-a-versa. As the side member 202 is moved relative to the bodymember 204, the reinforcement bar 224 and two lateral bars 226 engagethe center channel 228 and two side channels 230, respectively, in theside member 202. The implant 200 may also include at least one mechanismwhich may be in the form of a screw, stop pin, flange, lip, clip, orother mechanism that keeps the side member 202 from overextending anddisengaging from the base member 204.

Referring now to FIGS. 9 and 13-16, the implant 200 may also include atleast one movement mechanism 232. As best seen in FIG. 16, the at leastone movement mechanism 232 may, for example purposes, include two screws214, two threaded sleeves 218, and a gear rod 234 for extension andretraction of the side member 202 relative to the body member 204. Themovement mechanism 232 is configured to change rotational movement intotranslational movement. The movement mechanism 232 may also contain therotation mechanism 300. The gear rod 234 may include gear teeth 246 on afirst end and an opening 248 on a second end. The screws 214 may have ahead 236 on a first end and a threaded shaft 238 on a second end. Thethreaded sleeves 218 may include an interior threaded portion 220 thatis configured to engage with the screws 214 and a gear face 240 on theinferior end of the threaded sleeves 218 that is configured to engagethe gear teeth 246 on the gear rod 234. The interior threaded portion220 of the threaded sleeves 218 are configured to mate with the threadedshaft 238 of the screws 214. The interior threaded portion 220 of thethreaded sleeves 218 may be completely threaded or only partiallythreaded. Rotation of the gear rod 234 will cause the threaded sleeves218 to rotate which will in turn cause the screws 214 to move either inan inward or outward direction relative to the body member 204 therebyextending or retracting the side member 202 with the screws 214. As theside member 202 is extended or retracted the width of the overallimplant 200 will change. The side member 202 may also be extended orretracted by other means including, for example, a ratcheting or lockingsliding mechanism.

The gear rod 234 may be inserted into the opening 242 as shown in FIGS.9 and 12-13. The opening 242 runs along the longitudinal axis of thebody member 204. The body member 204 may also include two horizontalopenings 216 that may be positioned adjacent the through hole 206 andone of the through holes 208 in the body member 204. The two openings216 may extend along the lateral axis of the body member 204 andterminate in the opening 242. The openings 216 are configured to housethreaded sleeves 218. The openings may also have a groove or rim 244near the openings 216 for inserting a fastener, such as a c-clip, snapring, or the like, to secure the threaded sleeves 218 within theopenings 216. The rim 244 and/or fastener inserted into the rim 244 areconfigured to mate with a corresponding bearing surface on the threadedsleeves 218. The movement mechanism 232 for extension and retraction ofthe side member 202 relative to the body member 204 may be receivedwithin the openings 216 and the openings 212. The two openings 212 areexposed when the side member 202 is extended away from the body member204.

The head 236 of the screws 214 may be removably secured in the openings250 on the interior surface of the side member 202, as shown in FIGS. 13and 14. The screws 214 may be secured in the openings 250 with afastener, for example, a pin, clip, or the like. The openings 250 mayinclude a groove or rim 254 to retain the fastener and thereby removablysecure the screws 214 to the side member 202. The heads 236 may begenerally circular with at least one straight edge for mating with aprotrusion 252 in the openings 250 to prevent rotation and maintain theposition of the screws 214 as the threaded sleeves 218 rotate. The heads236 may also have other configurations, including but not limited tosquares, hexagons, and the like which inhibit rotation of the screws214. The heads 236 of the screws 214 may also be keyed to fit in aspecific orientation within the openings 250.

As shown in FIGS. 9-16, a rotation mechanism 300 may be used to expandand retract the side member 202 from the body member 204. The rotationmechanism 300 extends through an opening 242 in the body member 204which extends from the exterior of the body member 204 to engage thegear rod 234. The rotation mechanism 300 includes a toothed end 302 formating with the gear face 240 of the threaded sleeves 218 on theposterior side of the implant 200 and a driveshaft 304 which mates withthe opening 248 in the gear rod 234. The gear rod 234 in turn extendsthrough the opening 242 from the opening 216 on the posterior side ofthe implant 200 to the opening 216 on the anterior side of the implant200 where the gear rod 234 engages the gear face 240 of the threadedsleeve 218 housed in the anterior opening 216. The teeth or cogs 240 ofthe threaded sleeves 218 are sized to mate with the correspondingtoothed end 302 of the rotation mechanism 300 and the gear teeth 246 ofthe gear rod 234. Rotation of the rotation mechanism 300 by a user maybe accomplished by rotating the rotation mechanism 300 at the head 306which in turn will cause rotation of the toothed end 302 of the rotationmechanism 300 causing the posterior threaded sleeve 218 and the gear rod234 to rotate thereby rotating the anterior threaded sleeve 218.Rotation of the threaded sleeves 218 causes the screws 214 to translatein the threaded sleeves 218 thereby moving the side member 202. Thethreaded sleeves 218, screws 214, and gear rod 234 function to convertrotational movement of the rotation mechanism 300 to translationalmovement of the side member 202 relative to the body member 204. Thebody member 204 may also include an opening 258 extending through thetop and bottom bone contacting surfaces of the body member 204. Afastener, such as a pin, may be inserted into the opening 258 to securethe rotation mechanism 300 to prevent rotation after the desiredposition is reached. If the rotation mechanism 300 is secured by thefastener to prevent rotation, the rotation mechanism 300 may be leftinside of the implant 200 when the patient is closed after the surgeryis completed.

An inserter tool may be used to insert the implant 200 into a patientbetween two adjacent vertebrae. The inserter tool may be removablyattached to the implant 200 at an alignment buttress 256 on theposterior portion of the body member 204. The inserter tool may alsoprovide a mechanism to rotate the rotation mechanism 300 after theimplant 200 is inserted into the patient. Alternatively, a rotation toolmay be used to rotate the rotation mechanism 300 while the inserter toolholds the implant in a desired position.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprise” (andany form of comprise, such as “comprises” and “comprising”), “have” (andany form of have, such as “has”, and “having”), “include” (and any formof include, such as “includes” and “including”), and “contain” (and anyform of contain, such as “contains” and “containing”) are open-endedlinking verbs. As a result, a method or device that “comprises,” “has,”“includes,” or “contains” one or more steps or elements possesses thoseone or more steps or elements, but is not limited to possessing onlythose one or more steps or elements. Likewise, a step of a method or anelement of a device that “comprises,” “has,” “includes,” or “contains”one or more features possesses those one or more features, but is notlimited to possessing only those one or more features. Furthermore, adevice or structure that is configured in a certain way is configured inat least that way, but may also be configured in ways that are notlisted.

Although the example embodiments have been depicted and described indetail herein, it will be apparent to those skilled in the relevant artthat various modifications, additions and substitutions can be madewithout departing from its essence and therefore these are to beconsidered to be within the scope of the following claims.

What is claimed is:
 1. A surgical method for maintaining a space betweentwo vertebral bodies in a spine, comprising: obtaining a medical devicecomprising: a body member; at least one side member engaging the bodymember; and at least one movement mechanism engaging the at least oneside member and the body member, the at least one movement mechanismincluding first and second threaded rod members; inserting and couplinga tool into an opening within the medical device, the tool includingfirst and second sets of gear teeth; slidingly inserting the medicaldevice into a space between two vertebral bodies; and rotating the toolto move the at least one side member in a horizontal direction relativeto the body member, the rotating the tool including rotating the firstthreaded rod member with the first set of gear teeth and rotating thesecond threaded rod member with second set of gear teeth.
 2. The methodof claim 1, wherein the method further comprises inserting bone graftmaterial into the medical device.
 3. The method of claim 1, wherein themethod further comprises detaching the tool from the medical device andremoving the tool from the space between the two vertebral bodies in thespine.
 4. The method of claim 1, wherein the at least one movementmechanism includes first and second threaded sleeves, and whereinrotating the tool includes rotating the first threaded sleeve of incoordination with the second threaded sleeve.
 5. The method of claim 4,wherein the at least one movement mechanism further includes a gear roddrivingly engaged with the second threaded sleeve, and wherein rotatingthe tool includes: rotating the first threaded sleeve with the tool; androtating the second threaded sleeve with the gear rod.
 6. The method ofclaim 1, wherein the at least one movement mechanism includes first andsecond screw members and first and second threaded sleeves, and whereinrotating the tool includes threading at least one of the first andsecond screw members relative to at least one of the first and secondthreaded sleeves.
 7. The method of claim 1, wherein the inserting andcoupling the tool includes engaging the first set of gear teeth with afirst gear face coupled to the first threaded rod member and engagingthe second set of gear teeth with a second gear face coupled to thesecond threaded rod member.
 8. The method of claim 7, wherein the secondgear face is offset, in the horizontal direction, from the first gearface.
 9. A surgical method for implanting a medical device within aspace between two vertebral bodies in a spine, comprising: obtaining themedical device comprising: a body member; at least one moveable memberengaging the body member; and at least one movement mechanism engagingthe at least one moveable member and the body member, the at least onemovement mechanism including first and second threaded members;inserting and coupling a tool into an opening within the medical device,the tool including at least a first set of gear teeth; slidinglyinserting the medical device into a space between two vertebral bodies;and rotating the tool to move the at least one moveable member in afirst direction relative to the body member, the rotating the toolincluding rotating the first threaded member with the first set of gearteeth and rotating the second threaded member with a second set of gearteeth.
 10. The method of claim 9, wherein the inserting and coupling thetool includes engaging the first set of gear teeth with a first gearface on the first threaded member and engaging the second set of gearteeth included on the tool with the a second gear face on the secondthreaded member.
 11. The method of claim 9, wherein the inserting andcoupling the tool includes engaging the first set of gear teeth with afirst gear face on the first threaded member and engaging a gear roddisposed within the movement mechanism.
 12. The method of claim 11,wherein engaging the gear rod includes coupling a drive shaft portion ona distal end of the tool with an opening in a proximal end of the gearrod.
 13. The method of claim 11, wherein the gear rod includes thesecond set of gear teeth engaged with a second gear face on the secondthreaded member.
 14. The method of claim 9, wherein the first threadedmember includes a first threaded rod and the second threaded memberincludes a second threaded rod; and wherein the inserting and couplingthe tool includes: engaging the first set of gear teeth with a firstgear face disposed on a head of the first threaded rod, and engaging thesecond set of gear teeth with a second gear face disposed on a head ofthe second threaded rod.
 15. The method of claim 9, wherein the firstthreaded member includes a first threaded sleeve and the second threadedmember includes a second threaded sleeve; and wherein the inserting andcoupling the tool includes: engaging the first set of gear teeth with afirst gear face disposed on a first end of the first threaded sleeve,and engaging the second set of gear teeth with a second gear facedisposed on a first end of the second threaded sleeve.
 16. The method ofclaim 15, wherein engaging the second set of gear teeth includescoupling a drive shaft portion on a distal end of the tool with anopening in a proximal end of a gear rod, wherein the gear rod includesthe second gear face disposed on a distal end.
 17. The method of claim9, wherein rotating the tool to move the at least one moveable member inthe first direction includes engaging an externally threaded surface ofthe first threaded member with an internally threaded surface of a firstthreaded sleeve, and engaging an externally threaded surface of thesecond threaded member with an internally threaded surface of a secondthreaded sleeve.
 18. The method of claim 9, wherein rotating the tool tomove the at least one moveable member in a first direction includesengaging an internally threaded surface of the first threaded memberwith an externally threaded surface of a first threaded rod within thefirst threaded member, and engaging an internally threaded surface ofthe second threaded member with an externally threaded surface of asecond threaded rod within the second threaded member.